Physicist who inspired Interstellar spills the backstory—and the scene that makes him cringe

Interstellar, which opens this week, looks set to be one of the most talked-about films of 2014, not just because of its compelling storyline and dazzling special effects, but also for the fact that it sticks pretty close to established science and any speculation remains in the realm of plausibility. The man who inspired the film and kept a close eye on its scientific fidelity is Kip Thorne, a renowned theoretical physicist at the California Institute of Technology in Pasadena and one of the world’s leading experts in the astrophysical predictions of general relativity.

In 2006, Thorne and Lynda Obst, a longtime friend and film producer, wrote an eight-page treatment for a film that sprang from the astrophysics of black holes, wormholes, and time dilation. Steven Spielberg was soon on board to direct. Jonathan Nolan, who wrote films such as The Prestige and The Dark Knight Rises with his director brother Christopher, was working on the screenplay. Six years later, however, Spielberg had to drop out but was replaced by Christopher Nolan, director of the three Dark Knight movies and Inception.

The movie is set in a not-too-distant future, when various blights on crops have driven humanity to the brink of starvation and against science. A secret effort is under way to make a last-ditch attempt to find another planet that humans could colonize. Thorne has written about his experiences working with Hollywood and the scientific concepts addressed in the film in a book, The Science of Interstellar, to be published on 7 November. He spoke with ScienceInsider about the experience earlier this week. This interview has been edited for clarity and brevity.

Q: How much of your original treatment remains in the final film?

A: We wrote an original treatment, but it has changed so much that it’s not recognizable as the same movie except for the scientific vision and the venue, what I like to call the warped side of the universe—black holes, wormholes, higher dimensions, and so forth.

The story is essentially completely changed, except in the broadest brush sense that we had explorers leaving the Earth, traveling out to a wormhole in the outer parts of the solar system and through the wormhole, and visiting planets. Beyond that the story is truly the Nolans’ story. The thing that was preserved was the vision—the thing that was most important to Lynda and me—the vision of a movie in which real science, ranging from truth to speculation, is embedded deep into the movie’s fabric from the outset.

Also preserved were the guidelines we laid down from the outset. First, that nothing would violate established physical laws. Second, that all the wild speculations, and there certainly are some here, would spring from science and not from the fertile mind of a screenwriter. When I discussed those guidelines with Christopher Nolan at our first meeting in 2013, he said he liked them, to the extent that [they didn’t] get in the way of making a great movie. I do like what he did with the science. I’m very pleased with how it came out.

Q: Is there anywhere the moviemakers strayed outside your guidelines?

A: Not seriously. The one place where I am the least comfortable is on [a] planet where they have these ice clouds. These structures go beyond what I think the material strength of ice would be able to support. But I’d say if that’s the most egregious violation of physical law, they’ve done very, very well. There’s some artistic license there. Every time I watch the movie, that’s the one place where I cringe. I don’t think I’ve ever told anybody that.

Q: In your book, you say that Christopher Nolan introduced science elements of his own to the script. What did he bring?

A: The one that has the biggest impact, and that I really like, is the tesseract [the 4D analog of a cube]. When he told me in our first meeting that he was thinking of using a tesseract, he didn’t go into any detail. But I was very pleased because when I was 13 years old I read a book, One Two Three … Infinity by George Gamow, in which George drew a picture of a tesseract. It looks like two cubes, one inside another, and I spent hours staring at that, trying to come to grips with it. I found it so fascinating that it was one of the more significant influences on me to become a theoretical physicist.

So when he told me he wanted to use a tesseract, I thought that was great. I immediately saw and discussed with him how this was an ideal way to take his hero and carry him into the fifth dimension, and rapidly travel from one region of our universe to another, because distances in the [fifth dimension] will be much less than they are in our brane [our 4D slice of reality]. The tesseract that he created for the film is far more complex than any tesseract one has seen before. It’s fascinating; it’s beautifully designed.

Q: Where did the idea of blight-plaguing Earth come from?

A: This was due to [Jonathan Nolan]. When he introduced the idea, he and I and Lynda decided we really needed to find what was known about blight and other kinds of biological catastrophes, if they are to be responsible for diminishing the Earth to the degree you see in the film. We set up a “blight dinner” with biologists who were experts and we discussed this at length, trying to identify what things could go wrong with the biology of the Earth.

Q: You worked with the visual effects team at the company Double Negative in London, providing them with equations, which they then worked into their code. What was it like seeing those equations turned into the visual representation of a black hole?

A: It was wonderful to see the resolution they got. In practice I always did an implementation of the equation myself in Mathematica. I’m a real klutz computationally so Mathematica is just ideal for me. So I knew roughly what they were going to come up with, but it was just awe-inspiring to get back film clips from [Double Negative] and see this fabulous resolution and fabulous dynamics they were able to achieve.

Q: You’ve said that you learned something new from their simulations?

A: We learned [that] when you have a fast-spinning black hole, without any accretion disk, and let it just lens the distant sky—a star field—we saw a fantastically beautiful structure that is sort of like a fingerprint, but much more complex. We’ve long known that you’ll get multiple images of each star [around a black hole], due to [the combination of] light rays that come pretty much directly to the camera, [and] rays that go in and circle around the black hole once and come to the camera. But what we found was that on the side of the spinning black hole where space is moving towards us, [you see this beautiful structure].

It was completely unexpected with huge amounts of internal structure in it, regions where the star field appears to be quiescent and other regions where the stars seem to be whirling around in little vortices. To me it’s a lovely kind of discovery in the sense that it is really very beautiful and it arises from a collaboration between a scientist and a group of computer artists. We are submitting a paper about this and about the particular method that Double Negative uses to the journal Classical and Quantum Gravity.